Machine for sharpening four-face drills



April '12, 1960 TATAR 2,932,135

MACHINE FOR SHARPENING FOUR-FACE DRILLS File d Dec. 13, 1957 2Sheets-Sheet 1 April 12, 1960 A. TATAR 2,932,135

MACHINE 'FOR SHARPENING F OUR-FACE DRILL-S Filed Dec. 13, 1957 2Sheets-Sheet 2 INVENTOR A/romey United States Patent MACHINE FORSHARPENING FOUR-FACE DRILLS Claims priority, application SwitzerlandDecember 18, 1956 7' Claims. ((151-165) The present invention relates toa machine for sharpening four-face drills, which comprises a grindingwheel and a drill-carrying support articulated in such manner that thedrill can be displaced opposite the grinding wheel and can be broughtinto the various positions in which its different faces can be ground.

This machine is characterised by an abutment which is situated in the.working plane of the grinding wheel and against which the drill isbrought with a view to determining its axial position, and by an opticaldevice intended to collect the image of the drill bearing against thesaid abutment, the latter being transparent, and to project this imagewithin the view of the operator, this device comprising moreparticularly a reticle permitting the operator to bringthe drill into aspecific angular position, the whole arrangement being such as to permitthe axial and angular positions of the drill to be adjusted when it hasalready been placed on its support, and the drill to be checked afterthe grinding operations have been carried out.

One form of embodiment of the subject of the invention and a variationare illustrated by way of example in the accompanying drawings.

Figure l is a perspective schematic view of the machine.

Figure 2 is a perspective view of a grinding wheel itself, in whichvarious working axes of the machine have been indicated.

Figure 3 is a diagrammatic view in plan of part of the machine, adjustedfor grinding drills having a right-hand thread.

Figure 4 is a view similar to that of Figure 3 but regulated forgrinding drills having a left-hand thread.

Figure 5 is an axial diagrammatic view of the optical device of themachine,

Figure dis a plan view of the screen on which the enlarged image of thedrill is projected, and

Figure 7 is a diagrammatic view of a variation of the optical device.

The machine illustrated comprises a frame 1 on which is fixed anelectric motor 2 driving a grinding wheel 3 Whose working plane isdesignated as 4. The axial position of the grinding Wheel on the shaftof the motor can be adjusted by means of an adjusting screw 5. The frame1 comprises two lugs In between which there is articulated, about a pin6, a drum 7 belonging to the drill support. The pin 6 is parallel to theaxis of the grinding wheel, designated as 8 in Figure 2, andconsequently perpendicular to the working plane 4. The support of thedrill comprises also an L-shaped piece 9 which is rotatably mounted atone of its arms on the drum 7. This piece 9 is also capable of turningabout an axis 10 (Figure 2) situated in the working plane 4 of thegrinding Wheel. The drill support also comprises a second L- shapedpiece designated as 11, which is articulated at one of its arms on thepiece 9 about an axis 12 perpendicular to the axis 10. The drill 13isgripped by a Patented Apr. 12, 1960 clamp 14 which is fixed on thesecond arm of the piece 11, the axis 15 (Figure 2) of the drill beingthen perpendicular to the axis 12. The clamp 14 does not form part ofthe present invention and therefore has not been illustrated in detail.It is sufficient to indicate that it comprises on the one hand a mandrelgripping the body of the drill and on the other hand two elastic jawsgripping the drill in the immediate vicinity of its end at two points 16(Figure 6) diametrically opposite one another, situated on the lips ofthe drill, that is to say at two points where the drill is ground withgreat precision, thus ensuring its perfect centering.

The drum 7 carries a mark 17 opposite which moves a graduation 18 on thepiece 9, making it possible to determine the exact relative position ofthese two members. A locking mechanism (not shown) makes it possible forone member to be locked relatively to the other. Furthermore the piece 9has a graduation 19 opposite which moves a mark 20 carried by the piece11, which also makes it possible to determine their relative position.The piece 11 carries two adjustable abutting screws 21 which limititsrocking movements relatively to the piece 9. Finally, the clamp 14 ofthe drill 13 is mounted on the piece 11 of the drill support in suchmanner that its axial and angular positions can be regulated and thenlocked by means of an adjusting screw 22. It is also possible to releasethe clamp easily in order to allow it to turn on itself through Themachine is regulated by modifying the relative positions of the variousparts 'of the drill support; by rotating the L-shaped piece 9 relativelyto the drum 7 about the axis 10 situated in the working plane of thegrinding wheel, the angle of the drill point is modified. On the otherhand, by rotating the L-shaped piece 11 relatively to the piece 9 on theaxis 12 perpendicular to the axis 10 and to the axis 15 of the drill,the cutting angle and clearance angle of the drill are modified. In oneof the positions of the piece 11 hearing against one of the abuttingscrews 21, one of the two faces-tool face and back edge-of the drill isground whereas in the other position, wherein the piece 11 is bearingagainst the other abutting screw 21, thevother face is ground. Theposition of said abutting-screws is adjustable whereby the dihedralangle formed by the tool face and back edge of a drill can also beregulated. In order to grind the second pair of faces of the drill, itis necessary to cause the clamp 14 carrying the drill to rotate onitself through 180". Thus the complete grinding of a drill is carriedout in four passes, obtained by rocking the whole support about its pin6 whereby it is articulated on the frame; the two first passes areeffected in a given angular position of the clamp 14, each in twodifferent positions through 180, in the two same positions of the piece11 relatively to the piece 9.

It is indispensable that the initial position of the drill be exactlydetermined in the axial and angular senses. To this end, the machinecomprises a transparent plate 23 (Figures 1 and 5), which is situated inthe working plane 4 of the grinding wheel and against which the drill 13is made to abut when it is positioned with its clamp 14 on the support.The end of the drill is illuminated indirectly by a light source 24(Figure 5) which is not illustrated in Figure l and whose rays arereflected by a frustoconical mirror 25 onto the drill. The mirror 25could be dispensed with and the light source or sources could bearranged inside the frame of the machine behind the transparent plate23. An optical device, comprising a lens 26, a diaphragm 27 and a prism28, projects the enlarged image of the drill on a mat screen 29 (Figures5 and 6). This screen carries a reticle 30 by means of which it ispossible to adjust the angular position of the drill, until its centraledge coincides with one. of thelines. of the said reticle, as shown inFigure 6. The drill is then locked on its support, its angular and axialpositions being thus correct. to. check the drill after thegrindingoperations. havev been carried out.

The optical device, incorporated in the. frame of the, motor 2 of the.grinding wheel could be ofa differenttype (Fig. 7): lighting could, be.from, behind; the prism 28,-

could also be replaced by a mirror 31. 'In this latter. case, the matscreen could be dispensed, with and observation could be carried out bymeans of; an eye-piece 32 provided with a magnifying, glass, directlyonto the said mirror. The latter, and. also the abutment plate. 23,could then carry the reticle.

It. should be, noted that the machine can equally Well be employed forgrinding drills having a right-hand thread and also drills, having aleft-hand thread. To changeover from one to the other there is no needfor any dismantling or for replacing one part of the machine byanother.As will be seen from Figures 3 and 4 wherein the machine has beenillustrated diagrammatically for grinding righthand thread drills andleft-hand thread drills respectively, it is suiiicient to rotate thepiece 9 on the drum 7 through an angle of 90 and to cause the piece 11to rotate on the piece 9 through an angle of 180' in order to, changeover from one type of drill to another.

The advantages of the machine. described and illustrated are many: itsvarious elements form a compact whole, free from vibration, and havingno overhanging parts detrimental to precision of working. It permitsrapid adjustment of the point angle, the, cutting angle. and clearance,angle, so that the drills can be ground in accordance with thecharacteristics of the work to be effected. It is easy to manage anddoes not require any specially trained personnel. In this respect, theoptical device greatly facilitates the initial positioning of the drilland reduces the risks of error more particularly since. the angular andaxial positions of the drill are regulated When it is already inposition on the support. Finally, good visibility of working operationsis ensured whatever theface of the drill being worked, and this appliesequally Well to drills with a left-hand thread and to drills havingavright-hand thread.

What I claim is:

1-,. In a machine for grinding. four-face. drills, com- The, opticaldevice enables. moreover;

prising a frame, a grinding wheel and a drill-carrying support rockablymounted on said frame, around an axis parallel to the axis of thegrinding Wheel, so that the drill can be displaced opposite the grindingwheel and can be brought into various positions which permit its variousfaces to be ground, a transparent abutment which is situated in theworking plane of the grinding wheel and against which the drill isbrought with a view to determining its axial position, an optical devicewhich is intended to collect the image of the drill made to bear againstthe said abutment and to transfer this image to Within the operators.view, and a reticle in said optical device permitting the operator tobring the drill into a predetermined angular position, the whole in suchmanner as to permit the axial and angular position of the drill to beregulated when it is already in position on its support, ready for beingground, and the drill to be checked after the grinding operations havebeen carried out.

2. In a machine as claimed in claim 1, the feature that the opticaldevice is such that it presents to the operator an enlarged image of theend of the drill.

3. In a machine as claimed in claim 1, a mat screen in said opticaldevice on which the image of the point of the drill is projected.

4. In a machine as claimed in claim 1, a mirror and an eye-piece in saidoptical device, said eye-piece enabling to observe the image of thedrill reflected by said mirror.

5. In a machine as claimed in claim 1, the feature that the axis of theoptical device is refracted.

6. In a machine as claimed in claim 1, a light source in said opticaldevice, said light source illuminating the end of the drill.

7. In a machine as claimed in claim 1, a light source and afrustoconical mirror in said optical device, said frustoconical mirrorreflecting on to the end of the drill the rays of said light sourcewhich thus indirectly light up the end of the drill.

References Cited in the file of this patent V UNITED STATES PATENTSFrance Dec. 16, 1953

